No, I don't use the clay bar. I am not to keen on rubbing "clay" onto my Stang's paint. The clay stuff just sounds to harsh, if you will. I haven't really given it a chance though - maybe on my ZX2 first.
I have been using Liquid Glass Wash Concentrate, Pre-Cleaner, and their Liquid Glass "wax" (Not a wax, rather some type of polymer). I really like the results. No yellowing (big factor since I have an Oxford White Stang) and the hard clear coat that it leaves behind is very nice. You can even "wax" the pastic parts like headlights, tail lights, etc. My headlights look factory new after almost 10 years!! Very impressed with this.
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1991 5.0 LX Coupe
36,600 miles - Mint Condition
13.367 @ 104.90 mph w/ 2.130 60'
Pro-Charger D1-B on the way!!!